1. Field of the Invention
The present invention relates to heart surgery.
2. Description of the Related Art
Congestive heart failure affects 5 million people in the United States, and the NIH reports that 550,000 new cases are diagnosed every year (U.S.). World-wide, the figure is estimated at 22 million. Death rates have grown at an almost exponential rate. Congestive heart failure is the most common discharge diagnosis among Americans over age 65.
Congestive heart failure is a clinical syndrome with heterogeneous etiologies including ischemic cardiomyopathy, valve dysfunction, hypertensive cardiomyopathy, chemotherapy, alcohol abuse, radiation injury, idiopathic conditions, and others. Therapy is directed at the underlying cause, such as coronary revascularization, valve replacement, bi-ventricular pacing, and extensive drug usage, leveled at both the source and the symptoms. Unfortunately, the collective results of all available therapies in the treatment of congestive heart failure are disappointing. Pharmacology and electrical resynchronization have improved the symptoms in many cases, but direct approaches to improving the function of the weakened heart muscle, the common thread in all cases, are few.
Congestive heart failure is a syndrome characterized by inadequate cardiac output, regardless of primary cause. One common cause of congestive heart failure is a previous heart attack causing “ischemia,” or lack of oxygen to the heart tissue. Responsible for approximately two-thirds of congestive heart failure patients, ischemic cardiomyopathy follows a predictable course. Initially, there is an index event, most commonly an anterior myocardial infarction. When treated, the patient is stabilized, often receiving a balloon catheter dilitation, intra-coronary stent or bypass graft, and has an initially unremarkable recovery. However, over the next one to three years, a process known as “ventricular remodeling” takes place where the previously conical chamber becomes spherical and substantially dilated, and previously normal segments become acontractile. The syndrome of disabling, chronic, congestive heart failure begins. Drugs such as ARBs (angiotensin receptor blockers) and ACE (angiotensin converting enzyme) inhibitors have been shown to retard the progress of this disintegration of cardiac function, but the end result is delay, not cure.
One common symptom of many classes of heart disease is enlargement of the heart and/or dilation of the left ventricle. The cause of ventricular dilation is typically the result of a chronic volume overload or specific damage to the myocardium. If portions of the myocardium are damaged, increased requirements are put on the remaining healthy myocardium such that the heart may attempt to compensate with ventricular dilation and muscle hypertrophy. In diseased hearts, the compensation is not sufficient and the ventricular dilation and muscle hypertrophy progress to a point where efficiency of heart function begins to fall. Further attempts by the heart to compensate may accelerate this reduction in efficiency.
One surgical approach, the Dor Procedure (endoventricular circular patch plasty), has improved the course of the disease in selected congestive heart failure victims by excluding and reinforcing the dysfunctional, or akinetic, portion of the ventricle. That procedure typically involves the following steps:                Define the infarcted area on ventricular wall;        Incise through the infarcted area into the ventricle;        Open and secure the flaps of scarred ventricular tissue that were created during the incision;        Define the border around the viable and infarcted tissue in the ventricular wall; and        Place a Fontan stitch or purse-string suture around the circumferential margin where viable tissue meets the infarcted tissue and tighten the stitch like a noose, drawing the viable tissue closer together. (A second row of sutures may be required for further size reduction.)        
Optionally, the Dor Procedure may also involve suturing a patch of material (typically woven or knitted Dacron®, but others can also be used) on the inside of the ventricle, eliminating the defect in the ventricular wall defined by the tightened purse-string or strings.
While the Dor Procedure has benefits, it also has disadvantages. First, it is difficult for surgeons using the procedure to resize the ventricle to its natural size. In addition, the Dor Procedure requires surgeons to estimate the appropriate ventricle size for a particular patient. Some surgeons inaccurately estimate the appropriate ventricle size resulting in a ventricle that is too small, which may leave the patient clinically worse than before the procedure.
Dr. Dor has attempted to decrease the likelihood of achieving the result of an inappropriately small ventricle through using a fluid filled balloon as a guide for the practitioner when drawing the tissue together. The use of a balloon, however, has not adequately solved the problem. First, the practitioner must still estimate the appropriate size for the ventricle in deciding how much to fill and expand the balloon. Second, the balloon has the added disadvantage that a needle or any other sharp object used during the procedure may rupture the balloon and render it useless for the remainder of the procedure.
In addition to the Dor procedure described above, various other surgical approaches have been developed to treat dilation of the left ventricle of the heart (and the resultant CHF), by primarily restoring the size and volume of the diseased heart. Paramount to restoring normal heart function is identification and reconstruction of the apex. Apical reconstruction is important, because in the normal ventricle, the apex is functional and creates a vortex that helps cardiac muscle work. The new apex that is created during the ventricular reconstruction should prevent the ventricle from becoming spherical (again), a situation that may lead to creation of (or worsening of existing) mitral regurgitation. However, current approaches do not adequately provide for reconstruction of the apex of the heart. For example, failure to balance the position of the apex and volume has potentially deleterious impact on patient safety. A suboptimal short axis/long axis ratio, (i.e., apex improperly reconstructed too close to the mitral plane), may contribute to the development of late mitral regurgitation, even in cases where pre-existing mitral function is normal. The objective in optimizing the locus of the apex of the left ventricle should combine the optimal reduction of both the short axis with proper identification of the position of the new apex.
The position of the apex is important for normal functioning of the mitral valve. Ischemic functional mitral regurgitation is more frequent in dilated ventricles. In an enlarged heart, papillary muscles are displaced toward the lateral wall, losing their normal orientation toward the apex and increasing the distance between them. In this condition the posterior leaflet of the valve is retracted, the posterior annulus is dilated, and the valve becomes incompetent. Therefore this invention has the additional benefit of supporting proper mitral function.
It should therefore be understood that a device which can assist the surgeon to locate and anatomically configure the apex will provide a significant advantage to the surgeon and the patient. The invention disclosed here will cover the creation of new apex of a heart. In so doing, it will also direct the surgeon to proper size determination.